1. Mix the egg yolks, sugar, and cornstarch with 1/3 of the milk.
2. In a saucepan, boil 2/3 of the milk with the lemon peel and cinnamon.
3. After 3 minutes, remove from the heat and take out the lemon and cinnamon.
4. Slowly add the egg mixture to the hot milk through a strainer to ensure there are no lumps.
5. Return it to the heat until it boils, stirring constantly.
6. Once the mixture has begun to thicken, remove from the heat and put it into individual bowls to cool.
7. For an authentic finish, sprinkle with sugar and brown with a blowtorch or under a preheated broiler to caramelize.